The present invention relates to a magnetic recording/reproducing device such as a hard disk device and particularly to a magnetic recording/reproducing device using a composite head.
A magnetic recording/reproducing device such as a hard disk device is frequently used as an outer storage device having a large, which is capable of accessing at random. In recent years, high recording density for enlarging storage capacity has been greatly demanded, and the study and development have been made in various angles to meet the demand.
Generally, in the hard disk device, a plurality of magnetic disks, each which is formed on a non-magnetic substrate to have a magnetic layer, are stacked on one rotation spindle. A head for recording/reproducing is attached to an arm to be opposite to each disk surface. The arm is moved to a radial direction of the disk so that the head is positioned. In other words, a seek operation is executed. At a signal recording/reproducing time, the head slightly floats, and is placed to access to a predetermined position of the disk surface in such a state without directly contacting the disk surface rotating at high speed. Then, a signal is recorded onto a concentric track on the disk surface by the head, or the recorded signal is reproduced.
In order to meet the demand of high recording density for enlarging storage capacity, various trials have been made so far. For example, a linear recording density of the disk, that is, recording density in the length direction of the track is increased. Or, a track width is narrowed to increase the track density, thereby improving recording density. In recent years, for further improving the recording density, there has been enthusiastically made the study and development of a contact recording in which the head is floated extremely lower or the head is brought in substantially contact with a recording medium.
On the other hand, to improve sensitivity of a signal reproduction, an active typed head, e.g., an MR head using magnetoresistive effect, has been developed. The MR head is a head, which converts a magnetic flux sent from the recording medium to an electrical signal by use of a property in which an electrical resistance of a soft magnetic member such as permalloy is changed by an outer magnetic field. The MR head converts the change of the electrical resistance of an MR element formed of the soft magnetic member to a voltage change. Due to this, the sensitivity of the signal reproduction of the head is proportional to an amount of sense currents flowing to the MR element. As a result, even if a relative speed between the head and the medium is small, a large reproducing output can be obtained. Also, by use of the feature in which the reproducing output of the MR head is large, the track width can be narrowed to improve the track density.
The reproducing head, which is formed of the MR head, is frequently used to be combined with a recording head, which is formed of an inductive head, thereby forming a composite head. In this case, the reproducing head is combined with the recording head to be spaced from each other with a predetermined distance in the track direction. The composite head is mounted on a head slider. The composite head is moved in a radial direction of the disk by a rotary actuator through the head slider. Then, the positioning to a target track, that is, the seek operation is performed. At the seek operation time, a track shift occurs between the recording head and the reproducing head due to the space existing between the recording head and the reproducing head in the direction of the track. In this case, the track shift means that the relative position between the head and the track differs by depending on the recording head and the reproducing head.
The mechanism of the track shift will be explained with reference to FIGS. 1A and 1B. FIGS. 1A and 1B are views each schematically showing a state that the composite head moved by the rotary actuator is positioned at an inner peripheral track on the magnetic disk and an outer peripheral track. As shown in the figures, for moving the composite head by the rotary actuator, an angle difference between the direction of the head (azimuth direction) and the direction of the track, that is, skew angle, is changed by depending on the track radial direction where the head is positioned. In FIGS. 1A and 1B, a skew angle xcex8 is negative at the inner side (small diameter), and positive at the outer side (large diameter). The change of the skew angle appears as the track shift between the recording track and the reproducing track at it is. The track shift is increased as the track pitch is narrowed, and this brings about an obstacle to a correct reproduction.
Moreover, if the track width is narrowed to obtain high track density, it is necessary to increase the accuracy of positioning of the recording head and the reproducing head in the track width direction. However, if the track is narrowed, the tolerance between the recording head and the reproducing head in the positioning is relatively increased in view of the accuracy of the manufacturing process. This brings about an obstacle to obtain high track density.
Moreover, there is proposed a two-stage (two-dimensional) control typed head driving mechanism in which the rotary actuator is used as a coarse actuator and a mechanical fine actuator is used as a minor actuator. By use of this head driving mechanism, the composite head is controlled such that the recording head is mounted on the track at the recording time and the reproducing head is mounted on the track at the reproducing time. Due to this, for frequently repeating the recording and reproducing operations, the whole composite head must be frequently driven. As a result, it takes time to center a predetermined recording head or a reproducing head on a target track correctly.
In a case where the space between the head and the medium is extremely small and both contact with each other, its contacting force is added to the micro-actuator as disturbance. As a result, the head driving mechanism cannot be sufficiently functioned, and the tracking cannot be controlled with high accuracy.
Thus, in the magnetic recording/reproducing device using the composite head, there is the problem of the track shift. Then, the track shift causes the reduction of the reproducing output. Moreover, the track shift hinders the track pitch from being narrowed. Also, the track shift hinders the track density from being highly increased.
An object of the present invention is to provide a magnetic recording/reproducing device in which a track pitch can be narrowed, the high density of the track can be obtained, and a large reproducing output can be obtained.
The above object can be attained by the following magnetic recording/reproducing device:
Specifically, there is provided a magnetic recording/reproducing device comprising:
a recording head for magnetically recording a signal on a magnetic recording medium along a predetermined track;
a reproducing head, having a spin valve typed magnetoresistive element, for reproducing the signal recorded on the magnetic recording medium in which a sensitivity distribution in a track width direction is changed in accordance with an external control signal; and
controlling means for supplying the external control signal to the reproducing head.
The above-mentioned object can be also attained by the following magnetic recording/reproducing device:
Specifically, there is provided a magnetic recording/reproducing device comprising:
a recording head for magnetically recording a signal on a magnetic recording medium along a predetermined track;
a reproducing head, having a spin valve typed magnetoresistive element, for reproducing the signal recorded on the magnetic recording medium; and
a conductive member, magnetically associated with the magnetoresistive element, to which a current is supplied in accordance with time and positional behavior among the track, recording head, and reproducing head.
Moreover, the above-mentioned object can be attained by the following magnetic recording/reproducing device:
Specifically, there is provided a magnetic recording/reproducing device comprising:
a recording head for magnetically recording a signal on a magnetic recording medium along a predetermined track; and
a reproducing head member including a spin valve typed magnetoresistive element and bias magnetic applying means, associated with the spin valve typed magnetoresistive element, for applying a bias magnetic field to the spin valve typed magnetoresistive element, the reproducing head member for changing a sensitivity distribution in a track width direction based on a distance between the reproducing head and the recording head, and an angle difference between the direction of the reproducing head and the extending direction of the track.
Furthermore, the above-mentioned object can be attained by the following magnetic recording/reproducing device:
Specifically, there is provided a magnetic recording/reproducing device comprising:
a recording head for magnetically recording a signal on a magnetic recording medium along a predetermined track; and
a reproducing head including a spin valve typed magnetoresistive element and means for sending a current, for applying the bias magnetic field to the spin valve typed magnetoresistive element by a shunt bias effect, to the spin valve typed magnetoresistive element itself in which the current to be sent to the spin valve typed magnetoresistive element itself by the means is defined based on a distance between the reproducing head and the recording head, and an angle difference between the direction of the reproducing head and the extending direction of the track.
Thus, according to the present invention, a GMR head using the spin valve typed magnetoresistive element (GMR element) (to be specifically described later) is used as the reproducing head of the composite head. Then, the center of the sensitivity distribution of the GMR head is moved, so that a large reproducing; output can be obtained by use of the GMR head. Also, Moreover, even if the center of the sensitivity distribution is moved, the track pitch can be narrowed and the high density of the track can be obtained without largely generating the crosstalk between the tracks. The main feature of the present invention lies in the following point:
Specifically, the characteristic of the sensitivity of the GMR head is symmetrically shown. Then, even if the center of the sensitivity distribution is moved, the entire characteristic curve is moved without spreading the lower edge portion of the characteristic curve.
On the other hand, the sensitivity distribution of the reproducing head is controlled by the magnetic field applied to the spin valve typed magnetoresistive element. Thereby, as compared with the mechanical head drive mechanism, a servo zone, that is, a drive frequency band of the head can be greatly highly set. In other words, in the case of the conventional mechanical actuators such as the rotary actuator, the micro actuator, etc., the servo driving cannot be performed with a frequency exceeding 10 kHz. In contrast, in the system for magnetically moving the sensitivity distribution of the reproducing head according to the present invention, a driving object of the fine actuator function is the sensitivity distribution, which is a magnetic characteristic of the reproducing head itself. Therefore, unlike the mechanical actuator for driving the reproducing head itself, according to the present invention, since the driving object has no mass, the servo driving can be performed with a frequency higher by an order of magnitude than the case of using the mechanical actuator. As a result, the positioning control having extremely high response can be performed. Even in a case where the recording and reproducing are frequently repeated, it is possible to reduce a period of time, which is needed to center a predetermined recording head or reproducing head on a target track.
Moreover, if the sensitivity distribution of the reproducing head is magnetically moved, no unfavorable influence is exerted on the head driving even if disturbance caused by the mechanical contact between the head and the medium is added to the head. As a result, the head positioning control can be stably performed.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.